Specific question about Sound Transmission Class (STC) ratings in multifamily


I am not an architect or designer but was hoping someone might be familiar with STC ratings and enforcement for residential construction.

To provide some background: I live in an apartment building in Philadelphia, PA that was formerly an abandoned factory but since rehabbed (last year) into luxury flats. Unfortunately, my unit's bedroom shares a wall with my neighbor's bedroom, and the sound transfer is so bad, you can almost hear a pin drop (in their unit). You can imagine the privacy issues this causes. I have not yet notified my landlord because i want to prepare for the worst-case response ("sorry, deal with it"). As such, i am doing my research on building code as it is clear to me the contractor cheaped out on these partition walls.

I believe Philadelphia follows 2015 ICC standards for construction. The ICC states that walls between units must meet a 50 STC rating (if tested in a laboratory) or a 45 STC rating (if field tested).

My question is: If i were to conduct a professional STC test, and find the rating to be below 45 STC, would this be a violationg of building code and grounds for enforeceable remediation?

Thanks in advance for your help!

Nov 18, 19 12:56 pm

Not familiar with codes in Philadelphia... If it is a code issue, then I suppose the City could leverage the Owner to remedy the walls. That will likely require you to relocate for a bit while the work occurs. It might be better to leverage this as a means of getting out of your lease/rental agreement and live somewhere else. Field testing will require someone be on both sides of the wall, so you should discuss that with your neighbor. 

In defense of the Contractor, I imagine the Owner of the building is guilty of cutting corners on the cost of the partition walls if that is indeed what has occurred. 

Nov 18, 19 1:09 pm

See below...

Nov 18, 19 1:45 pm

Got it, do you happen to know if this only applies to new construction? This is a rehabbed building, not sure if that matters.


It doesn't matter if it is a rehabbed building. Bottom line- when you get a new CofO, the building needs to be brought up to code for the new use/occupancy.


You should look into when the conversion happened between factory and multi-family residential and see what code applied then... I'm pretty certain that this requirement hasn't changed in a while....

Nov 18, 19 1:46 pm

it happened last year! (2018)


I'd also look at the flooring and the ceiling. What materials are they? Are there major holes (ie - duct work, sprinkler lines, etc)? If it's an old factory, maybe there are steel beams running through. All of these items, and more, can negatively affect sound absorption/transmission. 

There are so many factors that go into a decent sound barrier. For the wall itself, you have improper installation of outlets, lack of sealing, etc at penetrations, maybe the contractor stuck regular insulation instead of sound insulation. 

Your options range from doing nothing to rebuilding the wall, to putting on iso-channel-shaded lipstick or quietrock-shaded lipstick, and others. 

Good luck!

Nov 18, 19 2:09 pm

This kind of thing can take a long time to be addressed by the city.  It's not an imminent life-safety issue so it won't get the highest priority.  Eventually the city will send an inspector.  If they do eventually find a violation, because it's not a life-safety issue they may or may not require the owner to fix it - in some cases they have leeway to issue fines (which will be paid to the city, and will not benefit you), or to require no remediation at all.  If they do issue a fine and/or require the owner to correct the problem there will be an appeal period.  If after that the owner is required to correct the problem they will be given a deadline - usually of several months and sometimes years - by which the changes must be made.

I wouldn't necessarily start with your own professional testing.  For your own sound testing to be taken seriously you'd need to hire a professional with a resume substantiating that they're an expert and regularly do this kind of work, and they'd need to show that their equipment has been calibrated recently.  But this testing could cost thousands of dollars, and the city may not accept your test results even if they do meet all these criteria. Also because of the way that sound measurements are averaged over periods of time, sporadic loud noises from next door may not exceed code limits, so aren't always actionable. 

I was involved in a project recently where there were complaints by one
business tenant about the noise from another business' equipment.  The few hours of testing to document that equipment noise from the
complaining tenant's premises by a professional was approximately $6500, and the results didn't prove the complaining tenant's case (because the noises that exceeded the allowable levels were of very short duration, but the overall averaged results were within limits.) It would be better to have the city do the testing, but they don't always have the equipment to do this properly.

Personally I might start with taking some un-official measurements with a phone, and paying a lawyer to write a letter to the landlord, angling for whatever outcome you're hoping for here, and see if you can negotiate a lease termination or some remediation.  If successful it will probably be a much shorter route for you, and if not successful you could escalate it to the city at that point.

Nov 18, 19 3:33 pm

Thanks for the advice. You make great points, some battles are just not worth it. For the record, i have reported this to the owner. They came out and inspected my unit and the neighbor's...their next steps were: "we are planning to consult the contractor".

Reading between the lines, it sounds like the ackowledge there is an issue. I have told them i would like to work with them to remediate (whether that means helping with the cost, staying in a hotel for a few days, etc.). I figured if they tell me to take a hike, i can at least let them know they are in violation of building code and perhaps they will reconsider. Worst, worst case, if they don't let me break the lease and refuse to fix the issue, i will add a layer of quietrock myself.

Non Sequitur

“i will add a layer of quietrock myself” - good luck with. You need to cut that shit with a table saw. It probably won’t do much for the installation effort and $.


I already got a reasonable quote to install a layer of green glue, quietrock and acoustic sealant along the joints and electric boxes. It's only a 12x14' wall. I believe it's worth it than having to pay movers and pay a tenant broker to find a new apartment. Not to mention i will (hopefully) no longer have to hear my neighbor's pillow talk.

Non Sequitur

^laminating gypsum board might not solve your problem if the sound leaking comes from multiple sources. If anything, the quietrock will help damper sounds from your side of the wall. Make a follow up post if you decide to install this.


Resilient channels, otherwise the vibrations may transfer.

Non Sequitur

Although you’re correct on the resilient channels, quietrock has a resilient core which acts as a substitute. It’s not cheap tho and I’m sure traditional 5/8” plus 7/8” resilient Chanel’s would be cheaper (and equivalent).


Sounds like you are on the right track trying to negotiate with the Builder.  Couple things to watch out for...

  1. You might not own the wall.  It could be part of the HOA communal property given it is between units.
  2. Be careful of signing anything if they do repairs.  Sometimes that fine print waives your rights with absurd indemnification clauses.  You don't want to do that for caulk.

And you can walk him through the pita.  If your only recourse is the courts, then that tends to expand rapidly.  Experts often see other things (it's what I do), the case expands, and instead of dealing with this one wall, they are now dealing with every common wall, floors, building shell, and the roof.  Most lawsuits start with a catalyst like this. And there's the issue with multifamily; if they screwed up your wall, I'd bet they repeated the same with every wall and every unit.  Based on my experience with accoustic engineer field tests, even walls built per the published STC theoretical won't ever pass (several reasons for that).  That GC really should want to avoid experts taking a close look.  That is assuming he had a good feel for the quality; which is the next issue in multi-family... the quality is 'low-bidder', fast turn-around, high ROI = typical subpar, even on high end market.  So it is in his interest to come to the table and negotiate while you are in the warranty period and he still has leverage with his subcontractors who performed the work.      

Nov 18, 19 6:54 pm
Non Sequitur

I think the OP is renting the space.


Thanks, just to clarify, this is a multifamily building, i am renting my unit. I can only guess this is an issue for other units.I really just want them to fix/resolve my bedroom wall so i don't have to move. If they tell me "too bad" and don't let me break my lease, that's when i will mention the code violation to hopefully get them to reconsider.


That is assuming they do have a code violation. You would be surprised that even with a code minimum (which developers typically go with) the sound is not contained and you can hear your neighbors. We run into that all the time as renters do complain all the time, even though it is built per code.


I'm certain this is well below the 45 STC rating required for field testing. I can hear whispering through the wall.


It's interesting, because in NYC we have a TR1 and TR8 form for special and progress inspections. There is no inspection for sound transmission or impact sound, so there is no way to verify if what was built is actually code-compliant. So the Architects/DOB do their "final" inspection not knowing if in reality their building is code compliant as far as noise is concerned.

Nov 19, 19 1:39 pm

Agreed. The problem with prescribed assemblies is that deals in theoreticals tested under laboratory conditions using a set sized panel and set test criteria (ASTM) that are known and designed for to get the rating. My jobsites look nothing like a lab, there are tons of other interfaces, and the 'noise' is a lot more dynamic... so the results seldom meet the theoretical ratings.... This is also a problem with testing; you have to follow the ASTM test, not just reality of a speaker system hung to the wall using screws to the studs that might be reality. So a poor performing wall can still pass the test but doesn't deal with how the space really works.


I don't know about Philadelphia, but in my city if you file a complaint the city inspector will come with a decibel meter, but he'll average the results over a 10 minute period.  If there's some type of near-constant noise then they might make the owner do something, but if it's hearing your neighbors' bedroom activity those neighbors would have to be quite loud, for a solid block of time, to get the city to do anything, not to mention that they'd have to be doing this sustained loud activity during the inspector's 9 to 5 Mon-Fri availability.  Do you get along with your neighbors?  If so maybe they'd willingly stage this demonstration. 

Nov 19, 19 1:53 pm

Oh yes, my neighbors have expressed similar concern. Timing the "sound test" would be easy. Thanks for the tip.

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